劍橋詞典a chemical element that is a radioactive gas formed when radium decays and found naturally in rock and soil 氡（鐳衰減時(shí)形成的一種放射性元素，發(fā)現(xiàn)自然存在於巖石和土壤中） Tests showed high radon levels . 試騐表明氡含量較高。 返回 radon